# 2196. Create Binary Tree From Descriptions from collections import defaultdict """ you are given a 2d integer array 'descriptions' where 'descriptions[i] = [parent_i, child_i, isleft_i]' indicates that 'parent_i' is the parent of 'child_i', in a binary tree of unique values. construct the binary tree described by 'descriptions' and return its root. the test cases will be generated such that the binary tree is valid. """ # Definition for a binary tree node. class TreeNode(object): def __init__(self, val=0, left=None, right=None): self.val = val self.left = left self.right = right class Solution(object): def createBinaryTree(self, descriptions): """ :type descriptions: List[List[int]] :rtype: Optional[TreeNode] """ children = set() m = {} for p, c, l in descriptions: np = m.setdefault(p, TreeNode(p)) nc = m.setdefault(c, TreeNode(c)) if l: np.left = nc else: np.right = nc children.add(c) root = (set(m) - set(children)).pop() return m[root] if __name__ == "__main__": obj = Solution() print( obj.createBinaryTree( descriptions=[ [20, 15, 1], [20, 17, 0], [50, 20, 1], [50, 80, 0], [80, 19, 1], ] ) ) print(obj.createBinaryTree(descriptions=[[1, 2, 1], [2, 3, 0], [3, 4, 1]]))